Taking puppies for a walk at Dream a Dream Dog Farm was one of the highlights of this trip. It was worth noting though, so you don’t trip and fall, that the roots of the trees are rise and fall at the surface of the ground making for a beautiful, though sometimes treacherous, sojourn.
When I asked about this phenomena, I was told that it was due to permafrost and the silt layers left over from glaciers that were here more recent than where I am from. This started a little study on my part. Permafrost is soil or silt that remains below 0° degrees Centigrade or 32° degrees Fahrenheit for at least two consecutive years. Many areas have experienced permafrost for over 10,000 years. Therefore trees in these areas must spread their root systems across the thin layers of top soil that there is and since the trees do grow so closely together the mass of roots gnarl and bulge about the surface frequently. Though quaintly beautiful, this causes the trees to be shorter in stature than others of their species.
This situation does cause some concern for the eco system in that when there is a warming system causing something called thermokarst, a ground slump caused by melting permafrost undermines the shallow root system causing the trees to lean or tilt the “drunken tree” effect seen in many spruce forests.
There is the concern by some people that global warming may melt the permafrost enough that the trees lose ground exposed to erosion therefore affecting the content of streams due to run off. The change in the chemical content of the streams could affect fish populations which could potentially affect the subsistence lifestyle still practiced in many areas of Alaska.
Birch or black spruce in bottomlands usually indicates permafrost within four to five feet of the surface and white spruce, poplar and aspen indicates the likelihood that permafrost is within two feet of the soil surface. An activity for your students may be to study topographical/vegetation maps to determine the depth of permafrost in certain areas.
Hope this starts some conversations,